The present invention relates to a pedestrian protection device for a motor vehicle, including a bumper crossmember on which a deformation element is arranged.
A known front end of a motor vehicle has, for example, a bumper crossmember which is fastened to front ends of longitudinal members, and a bumper cladding, wherein a soft foam which is deformable at a comparatively low load level is arranged between the bumper cladding and the bumper crossmember in order to protect pedestrians. On the basis of pedestrian protection, the soft foam is arranged in order to protect a pedestrian where appropriate against direct and immediate collision with a hard stiff structure, such as, for example, the bumper crossmember.
Furthermore, it is required for the motor vehicle to remain free from damage in a collision in a very low speed range of up to, for example, 4 km/h, in which the pedestrian protection is irrelevant because of the low speed.
Furthermore, at a somewhat higher speed, which is likewise still not relevant for pedestrian protection, such as, for example, of more than 4 km/h to less than 20 km/h, it is required that damage during a collision be small as possible and, for example, a radiator structure which is located in the front end region behind the bumper crossmember is not to be damaged.
In the event of a collision at a comparatively high speed which is no longer relevant for pedestrian protection, such as, for example, a speed of more than 50 km/h, a focus is on designing the motor vehicle and the crash structure thereof for occupant protection. For this purpose, the front end or vehicle front is designed in such a manner that it can absorb a large amount of collision energy by deformation over a certain deformation distance.
These different requirements are partially in conflict with one another and, up to now, have required a comparatively long vehicle overhang and therefore a higher weight and also a disadvantageous effect on the driving dynamics.
In order to address the resulting conflicting objectives, a bumper arrangement with a crossmember which is fastened to the vehicle body via crash boxes has been proposed, for example, in DE 102010054641 A1. A pedestrian protection element for soft impact of a pedestrian is formed in front of the crossmember in the direction of travel. In addition, a pivotable energy absorption element is provided which is pivotable in front of the pedestrian protection element and thereby permits increased energy absorption in collisions in which a higher collision energy absorption capability of the crash structure of the motor vehicle is required.
DE 102012112636 A1 likewise shows a bumper arrangement, including a bumper crossmember and a pedestrian protection element which can be switched over by means of an actuator from a stiff state into a comparatively soft state which serves for pedestrian protection.
A common feature of the bumper arrangements described in DE 102010054641 A1 and of DE 102012112636 A1 is that a crash or pre-crash sensor system and an actuator are required for this purpose, wherein, on the basis of the output signals of the sensor system, a switch can be actively made between a hard stiff state of the crash structure with high collision energy absorption capability and a soft state of the crash structure with low collision energy absorption capability in favor of pedestrian protection.
Furthermore, DE60316232T2 describes an impact energy transmission arrangement for a motor vehicle, including an elongate moveable element which is arranged in front of a bumper crossmember. The moveable element is movable collision-dependently either into a state in which it is moveable with little resistance, or into a state in which a movement is blocked in a form-fitting manner. The impact energy transmission arrangement has a stop element which is pivotable about an axis and has a first stop end and a second stop end. The first stop end serves for form-fitting engagement in the case of the collision in a low speed range of a motor vehicle of below approximately 20 km/h. The second stop end serves for form-fitting engagement in the event of the collision in a high speed range of above approximately 50 km/h. The form-fitting engagement here in each case brings about a high resistance in respect of a displacement of the elongate moveable element.
It is the object of the present invention to provide a pedestrian protection device for a motor vehicle, which is constructed even more simply, functions independently of a sensor system or an actuator, keeps the damage to the motor vehicle low at a low speed, is sufficiently soft for pedestrian protection at an average speed, and improves occupant protection at a high speed.
This and other objects are achieved by a pedestrian protection device for a motor vehicle in accordance with the embodiments of the invention.
The pedestrian protection device according to the invention for a motor vehicle, for example for a front or rear end of a motor vehicle, comprising a bumper crossmember has a deformation element which is arranged on the bumper crossmember and which has a first element and a second element which, in the event of a collision of the motor vehicle, are displaceable relative to each other, in particular in the direction of the bumper crossmember, and a mechanical locking mechanism. The locking mechanism has a moveable locking element which is pretensionable or pretensioned with a spring device which is arranged on the first element or the second element and is latchable in a form-fitting manner with a depression or step to the other of the first element and the second element. At a high displacement speed which is greater than or equal to a predetermined second displacement speed, the locking mechanism prevents a displacement of the first element relative to the second element by self-locking of the locking element. Furthermore, at an average displacement speed which is lower than the predetermined second displacement speed and greater than a predetermined first displacement speed, the locking mechanism permits a displacement of the first element and of the second element relative to each other. Furthermore, at a low displacement speed which is lower than or equal to the predetermined first displacement speed, the locking mechanism permits a displacement of the first element and of the second element relative to each other at least partially by the form-fitting latching of the locking element with the depression or step.
This means that a collision sensor system and an actuator system are not necessary for controlling locking of the locking mechanism. With just one locking element, using the mass inertia of the locking element, a damping force acting on the locking element, a friction force acting on the locking element and/or a contact force acting on the locking element, the deformation element can be switched in a simple way between a soft state, in which a relative displacement is permitted between the first element and the second element, and a stiff state, in which a relative displacement between the first element and the second element is prevented, depending on the displacement speed which arises through the collision or depending on the impulse associated therewith.
A relative displacement between the first element and the second element substantially takes place here in the longitudinal direction of the motor vehicle, which is customarily also a main direction during a head-on collision of the motor vehicle.
The locking mechanism according to the present invention automatically acts independently of a collision sensor system by, for example, using the mass inertia of the locking element. Furthermore, the locking mechanism acts independently of an actuator system. In other words, the locking mechanism is not driven by an actuator which permits or prevents a displaceability of the first element relative to the second element.
According to the invention, at the low displacement speed and therefore a low collision speed, the structure of the front end or of the rear end of the motor vehicle is of sufficiently stiff design that no structural damage, for example of the bumper cladding or the like, takes place due to excessive deformation. By this means, in the event of collisions at very low speed, such as, for example, in the case of what are referred to as parking dings or prangs, repair costs can be minimized and can be limited merely to repairing, for example, paint damage.
At the average displacement speed, and therefore at an average collision speed, in which pedestrian protection is relevant, the locking mechanism is unlocked and the length of the deformation element can be changed with a relatively low force in order to protect pedestrians, i.e. can be pushed together by relative displacement of the first element and of the second element with respect to each other.
At the high displacement speed, and therefore a high collision speed, at which occupant protection is relevant, the locking mechanism is impeded and the length of the deformation element can be changed only by plastic deformation or brittle failure, and therefore collision energy can be sufficiently absorbed by the deformation element. Self-locking takes place by means of a contact force between the locking element and the first element or the second element, wherein the contact force brings about tilting of the locking element.
The locking element and the spring device are advantageously designed in an interacting manner such that, with a displacement of the first element and of the second element relative to each other, the locking element is pretensionable by the spring device.
It is thereby possible in a particularly simple manner to achieve self-locking of the locking element. The spring device presses the locking element against an outer contour of one of the first element and the second element and thereby brings about contact forces which bring about tilting of the locking element such that the latter is not moveable further and therefore the movement of the first element and of the second element with respect to each other can be impeded.
Furthermore, the spring device can be substantially relaxed in a starting position. A starting position denotes the position of the pedestrian protection device before a collision of the motor vehicle.
This has the advantage that the spring device does not lose its spring tensioning force in the normal state.
According to a development of the pedestrian protection device of the present invention, the locking mechanism has a contact surface which is arranged and designed in such a manner that, upon a movement of the first element and of the second element relative to each other, the locking element is moveable along the contact surface in contact with the contact surface counter to the spring force of the spring device and is therefore pretensionable before the locking element reaches the form fit with the depression or the step. The contact surface is therefore in front of the depression or the step in the displacement direction. The spring device, the locking element and the contact surface interact here in such a manner that, at the high displacement speed, when the locking element is in engagement with the contact surface, a movement of the locking element along the contact surface and therefore a displacement of the first element and of the second element relative to each other is prevented by the self-locking of the locking element. At the average displacement speed, when the locking element is in engagement with the contact surface, a movement of the locking element along the contact surface is permitted, and, owing to a mass inertia of the locking element, the locking element, on leaving the contact surface, springs over the depression or step, and therefore does not latch into place in a form-fitting manner, and a further displacement of the first element and of the second element with respect to each other is permitted. And, at the slow displacement speed, when the locking element is in engagement with the contact surface, a movement of the locking element along the contact surface is permitted, and the locking element latches into place in a form-fitting manner with the depression or step at the slow displacement speed.
By way of the pretensioning of the locking element over the course of the collision at the low and the average displacement speed, the collision load is advantageously used for pretensioning the spring device. This creates an automatic passive mechanism which only uses friction forces between the locking element and the contact surface, a mass inertia of the locking element and/or a damping action of the spring element for its function. Accordingly, at the low displacement speed and therefore the low collision speed, latching into place takes place and the deformation element accordingly acts in a stiff manner. At the average displacement speed and therefore the average collision speed, the locking element does not latch into place because of its mass inertia and the other influencing variables mentioned at the average displacement speed, the locking element on the contrary passes during the relative movement of the first element and of the second element with respect to each other over the depression or the step without engagement and a further displacement between the first element and the second element is permitted, as a result of which the deformation element as a whole acts in a soft manner. At the high displacement speed, a movement of the locking element is impeded by high contact forces which are in action, and therefore, in turn, substantially no displacement of the first element in relation to the second element is permitted.
The contact surface is preferably designed obliquely with respect to a displacement direction of the first element and of the second element relative to each other. The contact surface here has a slope in the displacement direction of the locking element.
By way of the oblique design of the contact surface or the slope, the locking element can be progressively pretensioned with the spring device. Furthermore, by this measure, a contact force can advantageously act on the locking element during the collision.
According to a further preferred development, the deformation element is adapted in order, in a state of the locking mechanism, in which a displacement of the first element relative to the second element has been/is at least partially prevented by self-locking or latching, to absorb collision energy by plastic deformation and/or brittle failure of the deformation element over a predetermined deformation distance, for example within a range of 60 mm to 110 mm.
Accordingly, depending on the collision load and the speed during the collision, the deformation element can react in a sufficiently stiff manner and can transmit the collision load to the vehicle crash structure located therebehind, or a load threshold value of the self-locked or locked deformation element is exceeded, and therefore the latter is deformed and can thus absorb collision energy in order to protect other components and the vehicle occupants.
Preferably, in the event of the average displacement speed, at which the locking mechanism is neither self-locked nor latched, an energy absorption of the deformation element is lower than an energy absorption of the deformation element in the event of the low and high displacement speed.
Preferably, at the average displacement speed, the first element and the second element can be moveable relative to each other over a distance of 60 to 110 mm.
At the average displacement speed, the deformation element is therefore deformed at least over the distance provided for this purpose in order to protect a pedestrian at a relatively low load level.
The first element can be a cylindrical element which is displaceable in a corresponding guide of the second element. The locking element can be mounted on the first element or on the second element. In particular, the first element can be a hollow-cylindrical element. The first element here can have a circular cross section. The first element can preferably have a polygonal, in particular generally polygonal, cross section.
According to a preferred development of the pedestrian protection device, a deformation region of the deformation element can be formed between a bumper cladding and the bumper crossmember.
The second element is preferably secured on the bumper crossmember or is an integral component of the bumper crossmember.
Furthermore, the first element can be displaceable into an opening of the bumper crossmember.
By this means, a “soft” deformation region of the deformation element can be increased.
The spring device can additionally be provided with a damping device which suitably damps a movement of the locking element. Latching into place/non-latching of the locking element is therefore controllable in a suitable manner.
According to a further advantageous development of the pedestrian protection device, a deformation region of the deformation element is arranged on an outer side of the bumper crossmember. In the case of a front bumper crossmember, the outer side is the front side of the bumper crossmember. In the case of a rear bumper crossmember, the outer side of the bumper crossmember is the rear side of the bumper crossmember. In particular, the deformation region of the deformation element is formed between a bumper cladding and the bumper crossmember.
An advantage of the arrangement of the deformation element on the outer side of the bumper crossmember is that, in particular with respect to pedestrian protection, the deformation element directly protects the pedestrian by means of the soft structure. On the other hand, the bumper crossmember would have to be correspondingly softly mounted, wherein, in addition, a mass inertia of the bumper crossmember prevents direct soft flexibility.
The locking element is preferably mounted in a linearly moveable manner, in particular exclusively in a linearly moveable manner.
Above-cited developments of the invention can be combined as desired with one another in so far as is possible and expedient.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.